This section provides background information related to the present disclosure which is not necessarily prior art. This section provides a general summary of the disclosure, and is not a comprehensive disclosure of its full scope or all of its features.
Baseball pitching is one of the most unforgiving positions in sports; one mistake, like a hung curveball or a fastball that tails out over the plate and the result may be a run for the opposing team, or an injury to the pitcher. Because of this, there has been considerable scientific research conducted focusing on: (1) pitch aerodynamics, and (2) pitching mechanics. Despite this and other research, coaches still rely largely on a qualitative assessment of pitching mechanics and outcomes (in the form of radar gun measurements, ball and strike counts, and ERA) for pitcher training.
Studies investigating the effects of aerodynamics on a baseball's flight path consider how the ball's velocity and angular velocity at release causes it to break. Experiments reveal that the total break of the ball during free flight is proportional to the aerodynamic lift coefficient of the ball, is dependent on the seam orientation, and is a function of the magnitude and direction of the ball's angular velocity with respect to the velocity of its mass center. The orientation, spin, and velocity of the ball at release are controlled by pitching mechanics. These quantities ultimately differentiate one pitch type from another. The fastball and change-up possess pure backspin in relation to the velocity. In contrast, the curveball spins about the same axis as the fastball, but in the opposite direction, resulting in pure topspin. The slider is thrown with a combination of top- and side-spin.
Pitching mechanics studies have long relied on position data obtained via high-speed cameras. However, video-based motion capture is expensive, time consuming, and requires an operator skilled in both the collection and analysis of the data. Furthermore, baseball angular velocity is difficult to resolve using video based systems due to marker occlusion while the ball is in the pitcher's hand, and the high angular rate with which baseballs are thrown. For these reasons, using high speed video analysis systems in baseball pitcher training is not a viable option.
The advent of MEMS inertial sensors and MEMS-scale wireless transceivers has enabled an alternative to video-based motion capture. Several studies have explored the use of wireless inertial measurement units (IMUs) for baseball pitcher training. Unfortunately, the size and mass of the IMUs used in these studies (as well as those commercially available from companies like Xsens™) prohibit their use for measuring the motion of a baseball.
The present teachings address these shortcomings by presenting a highly miniaturized wireless IMU that is small and light enough to be embedded within a baseball (FIG. 1). The resulting design yields a low cost, highly portable and minimally intrusive approach for measuring the kinematics of the baseball during the pitching motion. While some ball spin rates remain outside the measurement range of most of today's technology for angular rate gyros, future advances of the present teachings, together with other methods, will allow ubiquitous application of the methods presented herein in the future.
Accordingly, the present teachings disclose a technology and method for calculating the kinematics of a baseball, softball, cricket ball and the like at all instants during a pitch and during the subsequent free flight of the ball using a miniaturized wireless inertial measurement unit embedded in the ball. The kinematical information can be used for training and evaluation purposes as well as a means to understand potential injury mechanisms. For instance, the methods allow one to determine the linear and angular velocity of the ball which define different pitch types and how well these different pitch types are thrown. The kinematical information can include any one of a number of useful parameters generally understood as kinematical information, such as, but not limited to, velocity, angular velocity, orientation, angular acceleration, linear and angular momentum, kinetic energy, position, and the like.
Presently, there is one product currently on the market that provides measurement of ball linear and angular speed. REVFIRE baseballs and softballs use a network of accelerometers embedded inside the ball's cover to deduce angular rate and linear speed. Angular rate is calculated by utilizing a proportional relationship between the g-forces on a spinning ball, measured by the accelerometer network, and the square of its spin rate. Linear speed is calculated by dividing a user entered throw distance by the time between ball release and impact. In essence, this product is able to provide the average magnitude of the angular and linear velocity vectors during ball flight, but not their directions or a full vectoral description of ball center velocity and ball angular velocity (vector-valued quantities). This fact renders the REVFIRE incapable of distinguishing pitch type (and hence training for specific pitch types) for lack of knowing the orientation of the ball angular velocity to the ball center velocity. Furthermore, the REVFIRE is only able to report average values for free-flight, it is unable to provide any information about how the pitcher develops the angular and linear velocity of the ball during the throwing motion. Thus the REVFIRE has far less utility for pitcher training.
Further areas of applicability will become apparent from the description provided herein. The description and specific examples in this summary are intended for purposes of illustration only and are not intended to limit the scope of the present disclosure.
Corresponding reference numerals indicate corresponding parts throughout the several views of the drawings.